How would the freebore in my Weatherby Accumark 300 Win. Mag. compare to any other factory 300 Win. Mag.? Is the excess freebore found in all the Weatherby rifles or just those chambered in Weatherby Magnum cartridges?

Hired gun is right , I've seen a couple Weatherby's that were chambered for standard rounds and their throats were cut normal length.
Part of weatherby mags get their extra velocity is from the freebore , the bullet is almost free from the case before it hits any resistance.